The present invention relates generally to adhesives and more particularly to acrylic adhesives with improved toughness, bond strength and resistance to moisture.
As used herein, xe2x80x9cacrylic adhesivesxe2x80x9d includes acrylate and methacrylate adhesives. Two-component, reactive acrylic adhesives are frequently used as structural adhesives in the transportation, automotive and general industrial markets. These adhesives offer structural bond strength, fast set time, and good resistance to temperature extremes. Acrylic adhesives, particularly methacrylate adhesives, are known in the art, which art is incorporated herein by reference; see for example U.S. Pat. Nos. 4,536,546; 4,714,730; 4,942,201; 4,769,419; 5,112,691; 5,206,288 and the patents cited therein, the contents of all of which are incorporated herein by reference.
In many applications, current acrylic adhesives lack sufficient toughness and/or bond strength. There is a need for reactive acrylic adhesives with improved toughness and bond strength. In addition, there is a need for such adhesives to have improved resistance to moisture.
The present invention provides an adhesive composition that includes about 10-90 weight percent ester monomer, about 2-85 weight percent polymeric elastomer, about 0.02-10 weight percent initiator, and about 1-80 weight percent vinyl-terminated liquid rubber. The ester monomer is selected from methacrylate ester monomers, acrylate ester monomers and mixtures thereof. The composition preferably contains about 0.1-5 weight percent phosphate ester. Preferably the initiator is in a peroxide paste which contains at least 5 weight percent organic peroxide and less than 18 weight percent water. A kit for providing a two-component reactive adhesive composition according to the invention is also provided.